1. Field of the Invention
The present invention relates to a sample detecting device. More particularly, the present invention relates to a high-density channels detecting device.
2. Description of Related Art
The thin film quality detecting technology, including measurements of optical constants, such as thin film thickness, optical refraction indexes, and extinction coefficients, plays an important role not only in semiconductor manufacturing processes, but also in liquid crystal display manufacturing processes.
Currently, the conventional thin film quality detecting device can be substantially classified into a single point thin film measuring device, a filtering image thin film measuring device and a multi-channel thin film measuring device, etc. FIG. 1 shows a single point thin film measuring device disclosed in U.S. Pat. No. 4,676,647. In the device, a light beam emitted from a light source 5 is irradiated to a sample 2 on a carrier 3, and the sample comprises a substrate or a thin film disposed on a substrate. The light beam is reflected by the sample 2, and then incident to a concave diffraction grating 8. A photodiode array detector 16 receives an optical signal, so as to obtain a reflection spectrum of the sample. Information of the single point film quality was acquired through a software algorithm. Though the architecture for the method is simple, a probe or the sample should be moved to collect the thin film information everywhere on the sample in order to obtain the information of the thin film quality of the whole test object, which takes a quite long time to detect. As a result, the method cannot be used in online detection.
FIG. 2 shows a thin film measuring device of filter image type, disclosed in U.S. Pat. No. 5,555,474. As shown in FIG. 2, the device mainly comprises a light source LS1, lenses L1 and L2, a filter wheel 24, a lens system 27, a beam splitter 26, etc. The filter wheel 24 is rotated during a measuring process. Since each filter 20 is a bandpass filter with different wavelength coverage from each other, after all filters 20 are rotated, a two-dimensional CCD 25 can shoot image information of a sample 23 at different wavelengths under different filters. The two-dimensional film quality measurement is obtained through a software algorithm. However, since rotating the filters takes time and the bandpass coverage of the filters is too broad, and the number of the filters is limited, the spectral resolution is low and the accuracy of the film quality measurement is limited. The two disadvantages both restrict the device to be used in online detection.
FIG. 3 shows a multi-channel thin film measuring device disclosed in U.S. Patent Application No. 20020030826. As shown in FIG. 3, the device utilizes a grating imaging spectrometer architecture. The parallel light reflected from the sample passes through a lens 34, a slit 35 and a lens 36, and then is incident to a grating 37. Subsequently, a detector 38 generates multiple spectral data. In FIG. 3, the perpendicular direction of the detector 38 represents the spatial direction, and the horizontal direction represents the spectral direction. With this device, the multi-channel spectral information (i.e., multi-point spatial information) can be obtained simultaneously, and the multi-point thin film quality measurement is also achieved. In general, the principle for operating a grating is that the light beam should be incident in parallel to the grating. But in FIG. 3, since the lens is placed in front of the grating 37, the light beam cannot be incident to the grating in parallel, thereby extra aberration will be generated and the spectral resolution is thus degraded. The measurable spectral range can be equally divided into only 32 parts and the spectral resolution is limited, thereby negatively affecting the accuracy of the thin film quality measurement. Therefore, the device cannot be used in online detection, either.
In recent years, since the area of a thin film sample has become larger and the processing speed is fast, rapid and accurate detection has become more and more important. However, the single point thin film measuring method is mostly used among the existing thin film quality detecting technologies. Though the method is accurate, the probe or the test object should be moved to obtain two-dimensional film images, which spends a lot of time and cannot be used in online detection. Though the multi-channel film quality detecting method is developed to detect more rapidly later, the measurement accuracy is low due to the aberration. Therefore, the method cannot be used in online detection, either.
In view of the aforementioned methods, no online thin film detecting device has achieved a multi-channel and rapid measurement as well as an accurate measurement of film quality. Therefore, up to now, no device has achieved the purposes of accurate measurement of thin film and rapid measurement. As a result, a new measurement method is highly desirable.